What is the max no of rows/records can be updated in Maintain at once? Does it lock records for others while I am updating it?

Thanks,
Jeeva

There is no maximum number of records that Maintain can update. If you have enough memory on your system, the amount of records is pretty much unlimited.

As for record locking, this depends on your database. Maintain respects the Change / Varify settings for your database whether it is FOCUS or RDBMS.